Multiple choice technology programming languages

Which is true? (Choose all that apply. )

  1. A. "X extends Y" is correct if and only if X is a class and Y is an interface

  2. B. "X extends Y" is correct if and only if X is an interface and Y is a class

  3. C. "X extends Y" is correct if X and Y are either both classes or both interfaces

  4. D. "X extends Y" is correct for all combinations of X and Y being classes and/or interfaces
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In Java, the extends keyword is used for inheritance between compatible types. A class can only extend another class, and an interface can only extend another interface. A class cannot extend an interface (it must use implements), and an interface cannot extend a class, making the other options incorrect.

AI explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) "X extends Y" is correct if and only if X is a class and Y is an interface - This option is incorrect. In Java, the keyword "extends" is used to indicate that a class is inheriting from another class or implementing an interface. Therefore, "X extends Y" is correct if X is a class and Y is either a class or an interface.

Option B) "X extends Y" is correct if and only if X is an interface and Y is a class - This option is incorrect. In Java, interfaces cannot directly inherit from classes. Instead, they can extend other interfaces. Therefore, "X extends Y" is incorrect if X is an interface and Y is a class.

Option C) "X extends Y" is correct if X and Y are either both classes or both interfaces - This option is correct. In Java, both classes and interfaces can extend other classes or interfaces. Therefore, "X extends Y" is correct if X and Y are either both classes or both interfaces.

Option D) "X extends Y" is correct for all combinations of X and Y being classes and/or interfaces - This option is incorrect. As mentioned before, interfaces cannot directly extend classes in Java. Therefore, "X extends Y" is not correct if X is an interface and Y is a class.

The correct answer is C. "X extends Y" is correct if X and Y are either both classes or both interfaces.

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